MICACEOUS SCHIST. 101 



things will often be found to prevail over considerable 

 tracts of country ; while, in the immediate vicinity,, 

 the beds are in their naturally straight order. These 

 curvatures, or contortions, must often exist where 

 they cannot be seen ; because the same set of beds, 

 traced on their prolonged edges, frequently present 

 reversed dips at the two extremities ; as happens on 

 a very large scale in Carityre. I may lastly remark, 

 that although granite veins traverse this rock in com- 

 mon with others, they do not abound in it as in 

 gneiss, for reasons which must now be apparent. The 

 veins of quartz, so common, often follow the flexures 

 of the rock itself, proving that they have been capable 

 of flexure, themselves ; while it is difficult to decide 

 whether they have been, in all cases, the produce of 

 aqueous infiltration. 



I have found considerable difficulty in satisfying my- 

 self respecting the cause of the laminar disposition in 

 this rock. In many cases, and particularly in the mi- 

 nute alternating strata, there is unquestionable evi- 

 dence that it is parallel to the plane of the bed, with 

 certain minute exceptions, arising from the undula- 

 tions of the larninse, equally occurring in argillaceous 

 schist, and even in secondary sandstone. In these, 

 the schistose structure, or the laminar tendency, bears 

 no necessary relation to the plane of the bed ; and the 

 same might therefore be imagined of micaceous schist. 

 But in schistose gneiss, to which this rock bears a 

 much nearer affinity, these are always coincident : so 

 that the same rule probably holds in this one also, 

 though not necessarily in all cases ; since, in the argil- 

 laceous schists, the laminar structure is sometimes 

 parallel, while, at others, it occupies different angles 

 with regard to the plane of the stratum. With re- 

 spect to the undulations and contortions of these, it is 



VOL. II. M 



